Odd artifact in mesh only when rendering in cycles, starts at third frame
One additional cut it solved.





But ... I cant find what it cause. I checked face orientation, shading type collision, make face planar, deleted all 88 thousand duplications (merge by distance), deleted all from scene (if it is not in hidden, isolated problematic face, unpluged material, tried Normals ... but nothing affect the issue. Only triangulation. Limited disolve to make n-gon back, brought issue back. Now Im interersted too :)

Definetely overlapping faces like n-gon tries to connect in two sharp angle?